Wind turbine blade

Abstract

A method of manufacturing a root ring for a wind turbine blade includes winding a metal sheet onto a mandrel to form a metal segment proximate a hub end of the root ring. A sheet-like fibrous material is also wound onto the mandrel to form a fibrous segment of the root ring proximate a distal end of the root ring. The metal sheet and the sheet-like fibrous material are interlaced to form a transition section of the root ring between the metal section and the fibrous section.

Description

Technical Field

[0001] The present disclosure relates to a wind turbine blade and a method of manufacturing a root ring for a wind turbine blade. Background Art

[0002] Wind turbine blades for large horizontal axis wind turbines have a significant mass, which may be in the range of 10 tons or more, up to 30 tons or more. The wind turbine blades are fastened to a pitch bearing of a hub to form a rotor that rotates on a main shaft to drive a generator.

[0003] The blades are typically connected to an inner or outer ring of the pitch bearing using a plurality of circumferentially spaced bolts extending into the root end of the blade in a direction parallel to the central axis of the root end of the blade. The stresses on the connection of the blade to the pitch bearing are considerable, mainly due to the blade mass and wind forces, but also the effects of the permanent rotation of the rotor, which tends to change the degree and direction of the forces acting on the blade with each rotation of the rotor. Vibrations in the system are also considerable.

[0004] For an expected life of 20 years or more, the fatigue performance of the blade to pitch bearing connection is critical. The bolt is usually connected to the blade root via a threaded metal bushing embedded in the fiber composite material at the root end of the blade. This bushing is usually cylindrical and usually made of steel. The bushing transfers the load from the composite material of the blade to the bolt, which then transfers the load to the hub via the pitch bearing.

[0005] The manner in which the blade root is connected to the pitch bearing is critical, given the load bearing and fatigue requirements placed on the connection of the blade to the pitch bearing. However, in known attachment methods, the component parts are not used in an optimal manner, resulting in excessive engineering and the use of large safety factors. For example, the bushings described above are typically held in place by adhesives, which are subject to constantly changing tensions during use. It is well known that adhesives are not optimally suited to such conditions. Similarly, the bolts connecting the pitch bearing to the blade are subject to tensile and bending loads, rather than the shear loads for which they are more suited.

[0006] It is desirable to increase the length of wind turbine blades so that each wind turbine can extract more energy from the wind to help reduce our reliance on fossil fuels. However, current methods of blade / hub connection as described above limit the extent to which this can be achieved.

[0007] Figure 1 A schematic diagram of a prior art wind turbine blade structure is shown. Figure 1The wind turbine blade 10 shown comprises a blade shell 13 consisting of a windward half shell 17 and a leeward half shell 18 connected together to form the blade shell 13. Both half shells comprise a fiberglass composite root 9 and the remainder of the half shells 17, 18 is made of glued wood and / or polyurethane foam core material adhered to a fiberglass composite skin.

[0008] Each half shell 17, 18 includes one or more spanwise extending beams or spar caps 22 to provide bending strength to the wind turbine blade 10. The spar caps 22 typically comprise a carbon fiber composite material due to the lightweight and rigid material properties of the material. Shear webs (not shown) extend between opposing spar caps 22 on the windward and leeward sides 17, 18 of the blade shell 13 and may be made of a glass fiber composite material. The shear webs carry the shear loads of the wind turbine blade 10.

[0009] The majority of the loads carried by the wind turbine blade 10 are carried by the spar cap 22 in a substantially straight load path. These loads must be transferred to the wind turbine hub via the root 9 and the pitch bearing. The root 9 is connected to the pitch bearing by a plurality of circumferentially spaced bolts 15 located in a ring around the root end 12 of the root 9. In order to avoid undesirable load peaks that could lead to material failure, the loads from the spar cap 22 must be spread out gradually around the entire circumference of the root end 12. In order to achieve this, a large amount of glass fiber composite material is required in the area between the end 24 of the spar cap 22 and the root end 12. Furthermore, the end 24 of the spar cap 22 must be positioned at a sufficient spanwise distance from the root end 12 so that the loads can be adequately distributed around the entire circumference of the root end 12. This is particularly important in view of the fact that the spar cap 22 is preferably disposed at a substantially straight load path. Figure 1 This is schematically indicated by the load line 20 .

[0010] It would be desirable to increase the amount of load that the root of a wind turbine blade can carry. However, current designs and construction methods of wind turbine blades limit the extent to which this can be achieved.

[0011] It is against this background that the present invention has been developed. Summary of the invention

[0012] The present invention provides a method for manufacturing a root ring for a wind turbine blade, wherein the root ring comprises a hub end and a tip end, and the root ring extends from the hub end to the tip end in the span direction, and the method comprises: winding a metal sheet onto a mandrel to form a metal segment near the hub end of the root ring; winding a sheet-like fiber material onto the mandrel to form a fiber segment near the tip end of the root ring; and interlacing the metal sheet with the sheet-like fiber material to form a transition segment of the root ring, wherein the transition segment is located between the metal segment and the fiber segment.

[0013] The method of winding the sheet onto a mandrel is advantageous because it allows for rapid formation of multiple layers without requiring extensive manual labor.

[0014] Optionally, the method comprises: overlapping the metal sheet with the sheet-like fiber material before winding the metal sheet and the sheet-like fiber material onto the mandrel. In this way, the metal and fiber sheets can be efficiently wound onto the mandrel in the same process step.

[0015] Optionally, the method comprises winding a layer of sheet metal material onto the mandrel before winding a layer of sheet fibre material onto the mandrel, thereby providing another option for manufacturing the root ring.

[0016] In one example, the method includes treating at least a portion of a surface of the metal sheet to change a surface finish of the metal sheet prior to winding the metal sheet onto the mandrel. Optionally, all or a portion of the surface of the metal sheet may be roughened prior to winding onto the mandrel. Treating all or a portion of the surface of the metal sheet may advantageously increase friction between layers of the metal sheet in the metal segment and help improve bonding between the metal sheet and the fiber composite material in the finished root ring.

[0017] The metal sheet may include a first portion positioned adjacent to a first edge of the metal sheet and a second portion positioned adjacent to a second edge of the metal sheet, wherein the thickness of the second portion gradually decreases from the first portion toward the second edge of the metal sheet, and the method includes: winding the metal sheet onto the mandrel so that the first portion of the metal sheet is located in the metal segment of the root ring and the second portion of the metal sheet is located in the transition segment of the root ring. In this way, the portion of the multi-layer metal sheet located in the transition segment gradually tapers from the metal segment toward the distal end of the root ring, thereby reducing the geometric stress concentrator between the transition segment and the fiber segment.

[0018] In one example, the sheet-like fiber material comprises a pre-impregnated sheet-like fiber material, wherein the method comprises: curing the pre-impregnated sheet-like fiber material after the pre-impregnated sheet-like fiber material has been wound onto the mandrel. Using a pre-impregnated sheet-like fiber material is advantageous because it does not require a separate resin impregnation step.

[0019] Optionally, the sheet-like fibrous material comprises dry sheet-like fibrous material, wherein the method comprises: impregnating the sheet-like fibrous material with resin after the sheet-like fibrous material has been wound onto the mandrel; and curing the resin. Depending on the design of the wind turbine blade, a resin infusion manufacturing method may be desirable.

[0020] Optionally, the method comprises: winding a sheet of fiber material having a greater thickness onto the mandrel at an end of the fiber segment near the distal end of the root ring than the sheet of fiber material wound onto the mandrel at an opposite end of the fiber segment near the transition segment, such that the thickness of the fiber segment gradually decreases toward the distal end of the root ring. In this way, the fiber segment of the root ring can be manufactured to have a tapered profile, which is advantageous when incorporating the root ring into a wind turbine blade.

[0021] The method may include machining the outer surface of the fiber segment to form a tapered wall thickness profile in the fiber segment of the root ring. Machining may be used to form a tapered segment from a non-tapered fiber segment, or a tapered fiber segment formed during winding may be further tapered and / or finished in the machining step.

[0022] On the other hand, the present invention provides a method for forming a wind turbine blade, the method comprising: forming a root ring using the above method; removing the root ring from the spindle; providing a windward half shell and a leeward half shell of a wind turbine blade shell, wherein the windward half shell and the leeward half shell each include a hub end and a tip end, wherein each half shell extends from the hub end to the tip end in the span direction; connecting the windward half shell to the leeward half shell to form a wind turbine blade shell; positioning the complete root ring at the hub end of the windward half shell and the hub end of the leeward half shell; and connecting the root ring to the windward half shell and the leeward half shell.

[0023] Optionally, positioning the root ring at the hub-facing end of the windward half shell and the hub-facing end of the leeward half shell includes positioning the root ring at least partially between the windward half shell and the leeward half shell.

[0024] Optionally, connecting the root ring to the windward and leeward shell halves comprises: laying one or more sheets of fibrous material over intersections between the root ring and the windward and leeward shell halves; and curing a resin impregnated or impregnated in the sheets of fibrous material.

[0025] In one example, connecting the root ring to the windward half shell and the leeward half shell includes connecting the root ring to one of the windward half shell or the leeward half shell and then connecting the root ring to the other of the windward half shell or the leeward half shell.

[0026] Within the scope of the present application, it is expressly intended that the various aspects, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular individual features thereof, may be adopted independently or in any combination. That is, all examples and / or features of any example may be combined in any way and / or combination, unless these features are incompatible. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Examples of the present invention are described below with reference to the accompanying drawings, in which:

[0028] Figure 1 A schematic diagram showing a portion of a prior art wind turbine blade structure;

[0029] Figure 2 A schematic diagram of a wind turbine is shown;

[0030] Figure 3 A schematic diagram of a wind turbine blade is shown;

[0031] Figure 4 a schematic cross-sectional view showing the root end of a wind turbine blade attached to an inner ring of a pitch bearing;

[0032] Figure 5 a schematic partial cross-sectional view showing an alternative root end configuration attached to an outer ring of a pitch bearing;

[0033] Figure 6 A schematic partial cross-sectional view showing another alternative root end configuration;

[0034] Figures 7a to 7c a schematic partial cross-sectional view showing a further alternative root end configuration attached to an alternative example of a pitch bearing;

[0035] Figure 8 A schematic diagram showing a portion of a wind turbine blade configuration;

[0036] Figure 9aA schematic isometric view showing a manufacturing method for a root portion of a wind turbine blade;

[0037] Figure 9b Shows Figure 9a A schematic cross-sectional view of a manufacturing method of;

[0038] Fig.9c Shown for Figure 9a A schematic cross-sectional view of a sheet metal material layer in a manufacturing method of; and

[0039] Fig.10 A schematic partial cross-sectional view of the root of a wind turbine blade is shown. DETAILED DESCRIPTION

[0040] The following detailed description refers to the accompanying drawings, which show, by way of illustration, specific details and examples in which the present invention may be implemented. These examples are described in sufficient detail to enable one of ordinary skill in the art to implement the present invention. Other examples may be used, and structural changes may be made without departing from the scope of the present invention as defined in the appended claims.

[0041] Figure 2 A wind turbine 1 is shown. The wind turbine 1 comprises a nacelle 2 supported on a substantially vertical tower 4, which itself comprises a plurality of tower segments 5. The nacelle 2 houses a plurality of functional components, including a gearbox and a generator (not shown), and supports a main rotor arrangement 6. The main rotor arrangement 6 comprises a hub 8 and a plurality of wind turbine blades 10 connected to the hub 8. In this example, the wind turbine 1 comprises three wind turbine blades 10.

[0042] Figure 3 A schematic diagram of a wind turbine blade 10 is shown. The wind turbine blade 10 comprises a blade shell 13 consisting of a windward half shell 17 attached to a leeward half shell 18. The wind turbine blade 10 extends from a root end 12 to a tip end 11, and each half shell 17, 18 has a tip end 19 and a hub end 21. The root end 12 is configured to be attached to a hub 8. A leading edge 14 and a trailing edge 16 extend in the spanwise direction between the root end 12 and the tip end 11.

[0043] Figure 4A schematic cross-sectional view of a root 29 of a wind turbine blade attached to an inner ring 41 of a pitch bearing 40 is shown. The root 29 comprises a tubular root portion having a proximal end 35 defining the root end 12 of the blade and a distal end 25 located at a spanwise distance X from the proximal end 35. The root 29 comprises a metal segment 30 extending from the proximal end 35 of the root 29 towards the distal end 25 of the root 29 and a composite fiber segment 32 extending from the distal end 25 of the root 29 towards the proximal end 35 of the root 29. A transition segment 31 extends between the metal segment 30 and the composite fiber segment 32.

[0044] The metal segment 30 is defined by a first portion 34 of a metal sheet 33. A second portion 36 of the metal sheet 33 extends from the first portion 34 into the transition segment 31 such that the metal sheet 33 extends from a proximal end 35 of the root 29 to an outermost spanwise end 37 of the transition segment 31 located a spanwise distance Y from the proximal end 35. The metal sheet 33 is bent about the spanwise axis 28 of the root 29 such that the metal sheet follows the circumferential curve of the root end 12.

[0045] The first portion 34 of the metal sheet 33 may have a constant thickness, while the second portion 36 may have a varying thickness that tapers from the first (or constant thickness) portion 34 toward the outermost spanwise end 37 of the transition section 31 .

[0046] The second portion 36 of the metal sheet 33 in the transition section 31 is encapsulated in a fiber composite material 38 that is continuous with the fiber composite material 38 of the composite fiber section 32. The thickness of the fiber composite material 38 in the transition section 31 varies along the length of the transition section 31, such that the total thickness of the fiber composite material 38 at the innermost spanwise end 39 of the transition section 31 is less than the total thickness of the fiber composite material 38 at the outermost spanwise end 37 of the transition section 31. Thus, the minimum thickness of the fiber composite material 38 in the transition section 31 is located near the thickest section of the metal sheet 33 in the transition section 31, while the maximum thickness of the fiber composite material 38 in the transition section 31 is located near the thinnest section of the metal sheet 33 in the transition section 31. In this example, the thickness of the root 29 may remain constant from the innermost spanwise end 39 of the transition section 31 to the outermost spanwise end 37 of the transition section 31. In other examples, the thickness of the root 29 may vary from the innermost spanwise end 39 to the outermost spanwise end 37 of the transition section 31, depending on design choice.

[0047] It should be understood that for the sake of clarity, Figure 4The thickness of the fiber composite material 38 shown in FIG. 3 is exaggerated, and the thickness of the transition segment 31 along its span may be substantially the same as the first portion 34 of the metal sheet 33 forming the metal segment 30. However, it should also be understood that this is not required, and that the relative thicknesses of the metal segment 30, transition segment 31, and composite fiber segment 32 need not be the same, depending on design choice.

[0048] The fiber composite material 38 is a glass fiber composite material, which is a commonly used material in the manufacture of wind turbine blades. However, any suitable fiber composite material may be used. In one example, the fiber material is a pre-impregnated fiber material. In another example, the fiber material is a dry fiber material that is impregnated with a resin and cured to form the composite material 38.

[0049] The metal sheet 33 is relatively thin relative to its spanwise dimension Y. For example, the thickness of the metal sheet 33 at the root end 35 may be 30 mm, and its spanwise dimension may be 650 mm. Preferably, the thickness of the metal sheet 33 is no more than 25% of its spanwise dimension. Preferably, the thickness of the metal sheet 33 is no more than 10% of its spanwise dimension, more preferably no more than 5% of its spanwise dimension, still more preferably no more than 1% of its spanwise dimension, and most preferably no more than 0.1% of its spanwise dimension. It is conceivable that the thickness of the metal sheet 33 at the root end 35 may be up to about 50 mm, and its spanwise dimension may be up to about 1000 mm. However, if the thickness of the metal sheet 33 does not exceed 25% of its spanwise dimension, dimensions outside this range may be used.

[0050] As will be described in more detail below, the metal sheet 33 can be formed by a metal sheet wound around a mandrel to form a tubular structure. Alternatively, the metal sheet 33 can be one of a plurality of metal sheets 33 arranged side by side to form a tubular structure. In each case, one or more metal sheets can be connected together by any suitable method, such as by welding or by interlocking formations located on the spanwise edges of the metal sheets. Alternatively, one or more metal sheets can be held in place by a fiber composite material 38 that encapsulates a variable thickness portion 36 of one or more metal sheets located in the transition section 31.

[0051] like Figure 4As shown, the metal segment 30 includes an outer circumferential surface 48 that contacts the inner circumferential surface 49 of the inner ring 41 of the pitch bearing 4. The metal segment 30 includes a plurality of bolt holes 46, which extend radially from the inner circumferential surface 47 of the metal segment 30 through the metal segment 30 to the outer circumferential surface 48 relative to the spanwise extension axis 28 of the metal segment 30. The metal segment 30 can be connected to the inner ring 41 of the pitch bearing 40 by radially extending bolts 45, which extend through the bolt holes 46 and enter the bearing ring 41. In this way, the bolts 45 are mainly subjected to shear loads, rather than tensile and bending loads as in the prior art connection method.

[0052] In reference Figure 4 In the depicted example, the root 29 is connected to an inner ring 41 of a pitch bearing 40. It will be appreciated that this is not essential and that the root 29 may be connected to an outer ring 42 of the pitch bearing 40 depending on the specific pitch bearing design.

[0053] The circumferential surfaces of the metal segments and the inner and outer rings are surfaces extending in the span direction.

[0054] exist Figure 4 4. In the cross-sectional view of the root 29, four bolts 45 are shown in line with each other. However, it should be understood that this is only an example and there may be only two bolts 45 or more than four bolts 45 in any particular spanwise section of the root 29. It should be understood that the metal segment 30 of the root 29 is connected to the inner ring 41 of the pitch bearing 40 by a plurality of bolts 45 spaced around the entire circumference of the metal segment 30. There is also a friction connection between the outer circumferential surface 48 of the metal segment 30 and the inner circumferential surface 49 of the inner ring 41. This friction connection is generated by the tension generated by the bolts 45 when they are tightened. Because the metal segment 30 and the bolts 45 are made of elastic metal material, the metal segment 30 and the bolts 45 are slightly deformed when the bolts are tightened, so that residual force is generated due to the elastic material of the metal segment 30 and the bolts 45 trying to restore their original shape. This is called "preload". The preload force pulls the inner ring 41 and the metal segment 30 tightly together, thereby generating friction between them. This frictional force serves to securely fix the metal segment 30 of the root 29 to the inner ring 41. This is an important contributing factor to the successful design and use of wind turbine blades of greater lengths than was possible with prior art connection methods.

[0055] In an alternative example, the metal segment 30 may be completely or partially covered by the fiber composite material 38, so that the inner ring 41 of the pitch bearing 40 contacts the fiber composite material 38 and does not contact the metal sheet 33 of the metal segment 30. In this case, the cross-sectional area of ​​the metal segment 30 in a direction perpendicular to its spanwise extension axis 28 may include at least 90% metal to generate and maintain the preload of the bolt 45 during the entire working life of the wind turbine blade 10. Preferably, the cross-sectional area of ​​the metal segment 30 may include at least 95% metal, more preferably at least 98% metal, most preferably at least 99% metal.

[0056] If the cross-sectional area of ​​the metal segment 30 comprises less than 90% metal, the above and Figure 4 The connection method shown is because the root 29 is still securely fixed to the inner ring 41 by the bolts 45 which mainly bear the shear load.

[0057] In the above example, the root 29 may be connected to the inner ring 41 or the outer ring 42 of the pitch bearing 40. It should be understood that the inner ring 41 or the outer ring 42 may include one or more components connected together to form a complete ring 41, 42. For example, the pitch bearing ring 41, 42 may include a plurality of components connected to each other. Figure 4 The same manner is described for a first portion connected to the root 29 and a second portion connected between the first portion and the remainder of the pitch bearing 40. The first and second portions of the pitch bearing rings 41, 42 may be connected to each other by any suitable method, including connection by circumferential surfaces in a manner similar to the connection between the root end 29 and the first portion of the inner ring 41 or the outer ring 42. Alternatively, the first portion may be connected to the second portion by stud bolts extending in the span direction. The use of pitch bearing rings 41, 42 comprising two or more components connected together is contemplated and applicable to all examples described herein.

[0058] Figure 5 Shows something like Figure 4 A schematic cross-sectional view of an example root structure of , in which the metal sheet 33 is replaced by a plurality of metal sheets 33. In this way, Figure 5 An example structure is Figure 4 A preferred example of an example structure of FIG.

[0059] Just as an example, Figure 5 The root portion 29 is attached to the outer ring 42 of the pitch bearing 40. It will be appreciated that in another configuration, the root portion 29 may be attached to the inner ring 41 of the pitch bearing 40. Note that like reference numerals are used throughout the specification to denote like components.

[0060] Figure 5 The root 29 is identical in all respects to Figure 4The root 29 is the same as Figure 5 The root 29 of the present invention comprises a plurality of metal sheets 33 arranged one on top of another. Thus, the root 29 comprises a metal segment 30 extending from a proximal end 35 of the root 29 to a distal end 25 of the root 29 and a composite fiber segment 32 extending from a distal end 25 of the root 29 to a proximal end 35 of the root 29. A transition segment 31 extends between the metal segment 30 and the composite fiber segment 32.

[0061] The metal segments 30 are defined by first portions 34 of the metal sheets 33. Second portions 36 of the metal sheets 33 extend into the transition segments 31 such that each metal sheet 33 extends from a proximal end 35 of the root 29 to an outermost spanwise end 37 of the transition segment 31 located a spanwise distance Y from the proximal end 35. The metal sheets 33 are bent about the spanwise axis of the root 29 such that the metal sheets follow the circumferential curve of the root end 12.

[0062] The first portion 34 of each metal sheet 33 may have a constant thickness, and each second portion 36 may have a variable thickness that gradually decreases from the constant thickness portion 34 toward the outermost spanwise end 37 of the transition section 31 .

[0063] The second portion 36 of the metal sheet 33 in the transition section 31 is encapsulated in a fiber composite material 38 that is continuous with the fiber composite material 38 of the composite fiber section 32. The second portion 36 of each metal sheet 33 is interlaced with the fiber composite material 38 in the transition section 31. Figure 5 In the example shown, the fiber composite material forms the outermost layer of the transition section 31. In an alternative example, the second portion 36 of the metal sheet 33 may form the outermost layer of the transition section 31.

[0064] The metal sheets 33 are relatively thin relative to their spanwise dimension Y. For example, the thickness of the metal sheets 33 may be 3 mm, and their span length may be 650 mm. Preferably, the thickness of the metal sheets 33 is not greater than 25% of their spanwise dimension. More preferably, the thickness of the metal sheets 33 is not greater than 10% of their spanwise dimension, still more preferably not greater than 5% of their spanwise dimension, further more preferably not greater than 1% of their spanwise dimension, and most preferably not greater than 0.1% of their spanwise dimension. It is conceivable that the thickness of the metal sheets 33 may be as low as 0.5 mm, and their spanwise dimension may be as low as 100 mm. However, if the thickness of the metal sheets 33 does not exceed 25% of their spanwise dimension, dimensions outside this range may be used.

[0065] The metal sheet 33 may be formed of a continuous sheet of metal that is spirally wound around a mandrel to form a tubular structure. Alternatively, the metal sheet 33 may include a plurality of metal sheets 33 that are arranged side by side and one above the other to form a tubular structure. In this case, the metal sheets 33 may be offset relative to each other around the periphery of the tubular structure so that the edges of the metal sheets 33 in one layer are not aligned with the ends of the metal sheets 33 in the adjacent layer. The metal sheets 33 may be connected together by any suitable method, such as by welding or by interlocking formations located on the spanwise edges of the metal sheets 33. Alternatively, the metal sheets 33 may be held in place by a fiber composite material 38 that encapsulates a second portion 36 of the metal sheet 33 located in the transition section 31.

[0066] As above about Figure 4 As stated, Figure 5 A preferred example includes a plurality of bolt holes 46 extending through the metal segment 30. The metal segment 30 is connected to the outer ring 42 of the pitch bearing 40 by bolts 45 extending radially.

[0067] As above about Figure 4 As discussed in the example of , a friction connection also exists between the inner surface 47 of the metal segment 30 and the outer surface 50 of the outer ring 42. A friction connection also exists between the contact surfaces of the plurality of metal sheets 33. As discussed above, when the bolt 45 is tightened, a friction connection is created by the preload of the bolt 45.

[0068] In an alternative example, the metal segment 30 may include a small amount of composite material 38 between one or more metal layers of the metal segment 30 and / or on the outermost metal layers. In this case, the cross-sectional area of ​​the metal segment 30 in a direction perpendicular to the spanwise extension axis of the metal segment 30 must include at least 90% metal to generate and maintain the preload of the bolt 45 throughout the working life of the wind turbine blade 10. Preferably, the cross-sectional area of ​​the metal segment 30 may include at least 95% metal, more preferably at least 98% metal, and most preferably at least 99% metal. As described above with respect to Figure 4 As discussed above, if the cross-sectional area of ​​the metal segment 30 comprises less than 90% metal, the above and Figure 5 The connection method shown is because the root 29 is still securely fixed to the outer ring 42 by the bolts 45 which mainly bear the shear load.

[0069] Figure 6 Another example of a root 29 is shown, which is similar in all respects to the Figure 5 The root 29 is the same as that of the transition section 31, except that the cross-sectional profile of the metal sheet 33 is the same as that of the transition section 31. Figure 5 The cross-sectional profile of the example is different. Thus, Figure 6 An example structure is Figure 5A preferred example of an example structure of FIG.

[0070] exist Figure 6 In the example of FIG. 4 , the first portions 34 of the metal sheets 33 may each have a constant thickness and a textured second portion 36 extending into the transition section 31 .

[0071] In this example, the outer surface of the second portion 36 of the metal sheet 33 includes a plurality of formations 53 extending radially relative to the spanwise extension axis of the metal segment 30. The radially extending formations 53 include a plurality of discrete protrusions that generally have a thorn-like configuration. It should be understood that the formations 53 may have any suitable shape, including, for example, cylindrical, circular, or square sides. In another example, the formations 53 may be formed by roughening the surface of the second portion 36 of the metal sheet 33. In another example, the formations 53 may include parallel or intersecting grooves, such as those found on a file or rasp.

[0072] The second portion 36 of the metal sheet 33 located in the transition section 30 is encapsulated in a fiber composite material 38 that is continuous with the fiber composite material 38 of the composite fiber section 32 of the root 29. The second portion 36 is interlaced with the fiber composite material 38 in the transition section 31. The formation 53 helps improve the integrity of the connection between the fiber composite material 38 and the second portion 36 of the metal sheet 33. However, it should be understood that the formation 53 is not required, and some or all portions of the metal sheet 33 located in the transition section 31 may not include the formation 53. Similarly, each side of the second portion 36 does not have to include the formation 53, and in some examples, only one side of the second portion 36 may include the formation 53.

[0073] In one exemplary construction method, the depth of the fiber material may match the depth of the step 51 located in the metal sheet 33 at the spanwise outermost end 54 of the metal segment 30, and the depth of the spanwise outermost end 52 of the second portion 36, so that during layup, the fiber material may be easily interleaved with the second portion 36. For example, the step 51 may have a depth of 0.5 mm, the second portion 36 may have a depth of 0.5 mm (excluding the formation 53), and the fiber material may have a depth of 0.5 mm. However, this is not required, and any other suitable dimensions and layup methods may be used.

[0074] The metal sheets 33 are relatively thin relative to their spanwise dimensions. For example, the metal sheets 33 may be 1.5 mm thick at the proximal end 35 of the root 29, and their spanwise dimensions may be 650 mm.

[0075] Figures 7a to 7c Shows Figure 5A schematic partial cross-sectional view of another example variation of the root structure of. Figure 7a In the example of Figure 4 and Figure 5 The inner ring 41 of the bearing 40 is attached to the inner ring 41 of the pitch bearing 40 in the same manner as discussed above. In this example, the metal sheet 33 of the metal segment 30 includes a formation 56 that engages with a complementary formation 56 located on an adjacent layer of the metal sheet 33. In addition, the inner surface of the bearing inner ring 41 may include a complementary surface formation 57 that engages with the surface formation 56 of the metal segment 30.

[0076] The surface formations 56 provide an interlock between adjacent layers of the metal sheets 33 and an interlock between the outer surface of the metal segment 30 and the inner surface of the inner ring 41 of the pitch bearing. Figure 7a In the example shown, radially extending bolts 45 are shown connecting the metal segment 30 to the inner ring 41. However, the bolts 45 may be omitted, the connection between the root 29 and the inner ring 41 being provided entirely by the interlocking formations 56,57.

[0077] exist Figure 7a In the example of FIG. 4 , the innermost surface 47 of the metal segment 30 is shown as having a formation 56. It should be understood that, alternatively, the surface may not include the formation 56.

[0078] like Figure 7a The portion of the metal sheet 33 shown in the transition section 31 of the root 29 can be similar to the above description of Figure 5 In another example, the portion of the metal sheet 33 located in the transition section 31 may also include a formation 56 to help improve the connection between the metal sheet 33 and the fiber composite material 38. The formation 56 in the metal segment 30 and optionally in the transition section 31 may include the same as described above with respect to Figure 6 The discrete formations 53 described may alternatively be continuous formations, such as curves or waves. Alternatively, the formations 56 may be formed by roughening the surface of the metal sheet 33 (e.g., by sandblasting). In another example, the formations 56 may include parallel or intersecting grooves, such as those found on a file or rasp.

[0079] exist Figure 7b In the example of Figure 5 Same as above, and Figure 4 and Figure 5The same manner as described is attached to the inner ring 41 of the pitch bearing 40 by bolts 45. In this example, the inner ring 41 is elongated and includes a proximal end 60 and a distal end 61, the proximal end 60 defining the hub end of the bearing inner ring 41 and the distal end 61 being located at a spanwise distance from the proximal end 60. A hub section 62 of the bearing inner ring 41 extends from the proximal end 60 to the distal end 61, while a blade section 63 of the bearing inner ring 41 extends from the distal end 61 to the proximal end 60.

[0080] The outer circumferential surface 48 of the metal segment 30 contacts the inner circumferential surface 49 of the inner ring 41 only in the blade-facing section 63 of the inner ring 41, so that the contacting circumferential surfaces 48, 49 are completely located in the blade-facing section 63. The hub-facing section 62 of the inner ring 41 operatively engages the outer ring 42 of the pitch bearing 40 via a bearing element (e.g., spherical roller) 43 located between the inner ring 41 and the outer ring 42 of the pitch bearing 40. This arrangement helps to decouple the loads transmitted from the root 29 to the inner ring 41 from the bearing element 43, thereby reducing the forces encountered by the bearing element 43 in use.

[0081] Figure 7c An example similar to Figure 7b In the example of the present invention, in addition to the bearing ring inner 41 including an annular groove 70, the metal segment 30 of the root 29 is accommodated in the annular groove 70. In this example, the metal segment 30 of the root 29 can be connected to the inner ring 41 by bolts 45 alone (mainly bearing shear forces), or the bolts 45 can be preloaded as described above to generate friction between multiple layers and between the circumferential outer surface of the metal segment 30 and the circumferential inner surface of the groove 70.

[0082] In this example, and in all the examples described above, the metal segment 30 of the root 29 may be attached to the inner ring 41 or outer ring 42 of the pitch bearing 40 by a shrink fit connection, in which the inner ring 41 or outer ring 42 is heated to expand it, the metal end 30 of the root 29 is positioned in or around the inner ring 41 or outer ring 42, as the case may be, or in the groove 70, and the rings 41, 42 are allowed to cool so that a shrink fit connection is formed between the rings 41, 42 and the metal segment 30 of the root 29. This may also be achieved by cooling the metal segment 30 of the root 29 and rewarming it before positioning the metal segment 30 of the root 29 in or around the rings 41, 42. If a shrink fit connection is used, the bolts 45 may be omitted. Alternatively, bolts 45 may be used for additional safety.

[0083] Now refer to Figure 8 , shows a schematic diagram of a wind turbine blade 10 including a root portion 29 connected to a blade shell 13. The root portion 29 is as described above with reference to Figures 4 to 7cBecause the metal section 30 of the root 29 is much stiffer than the glass fiber root of the prior art, the spanwise innermost end 24 of the carbon fiber spar cap 22 can be located closer to the root 29 than was possible in the prior art. As a result, the stiffness of the entire wind turbine blade 10 is increased because the carbon fiber spar 22 can extend closer to the stiffer root 29. This is beneficial for the efficiency of the wind turbine blade 10. The metal section 30 of the root 29 is able to withstand higher peak loads than the glass fiber root of the prior art could withstand. This is beneficial because it allows less glass to be used in the construction of the root 29, thereby providing cost and environmental benefits.

[0084] In addition to these advantages, the root configuration described above has the additional advantage that the integrity of the bond between the various layers of the root wall can be interrogated throughout its depth by ultrasonic non-destructive testing (NDT) methods. This is not possible with a root comprising conventional spanwise extending bolt holes, as the ultrasonic NDT equipment cannot be "unaffected" by the voids formed in the glass fiber composite material in which the insert for the stud insert is accommodated.

[0085] Figure 9a The root ring 80 is shown (see Fig.10 ), Figure 9b Shows Figure 9a Schematic cross-sectional view of the manufacturing method. Fig.10 Shown by Figure 9a and Figure 9b Schematic cross-sectional view of a root ring 80 manufactured by the method.

[0086] As will be described in more detail below, the root ring 80 is incorporated into the stack of blade shells 13 to form the root 29 of the completed wind turbine blade 10. As such, the root ring 80 includes a hub end 81 and a tip end 82 (relative to the position of the root ring 80 in the completed wind turbine blade 10) extending from the hub end 81 to the tip end 82 in the spanwise direction.

[0087] The root ring 80 is formed with a plurality of metal sheet layers 33 arranged one on top of another so that the root ring 80 when incorporated into the blade shell 13 forms a blade shell as described above with reference to FIG. Figures 5 to 7c The root 29 is depicted. The completed root ring 80 includes a metal section 30, a transition section 31 and a composite fiber section 32.

[0088] Reference Figures 9a to 9c , the root ring 80 is manufactured on the mandrel 90 by interlacing and winding the metal sheets 33 and the sheet-like fiber material 98 around the mandrel 90. Once wound onto the mandrel 90, the metal sheets 33 form the metal sheet layers of the root ring 80. Figure 9b Only the metal sheet 33 wound around the mandrel 90 is shown in FIG. 1 , since the cross section is taken through a plane of the mandrel 90 corresponding to the location of the metal segments 30 forming the root ring 80 .

[0089] like Fig.9c As shown, the metal sheet 33 may include a first constant thickness portion 34 and a second variable thickness portion 36. The metal sheet 33 is wound in layers on the mandrel 90 such that the first portion 34 forms the metal segment 30 of the root ring 80 and the second portion 36 is located in the transition segment 31 of the root ring 80.

[0090] The metal sheet 33 may have a thickness of 3 mm throughout the first portion 34 and have a spanwise dimension Y of 650 mm. For example, if 10 layers of such a metal sheet 33 are wound onto the mandrel 90, the metal segment 30 of the root ring 80 will have a radial depth (relative to the spanwise extension axis of the root ring 80) of 30 mm, and the transition segment 31 will include 18 to 20 metal-to-composite fiber interfaces 83 (depending on the material forming the outermost layer of the transition segment 31).

[0091] In another example, the metal sheet 33 may have a thickness of 0.5 mm throughout the first portion 34 and have a spanwise dimension Y of 650 mm. If 60 layers of such metal sheet 33 are wound onto the mandrel 90, the metal segment 30 of the root ring 80 will have a radial depth of 30 mm as previously described, but the transition segment 31 will include six times the number of metal to composite fiber interfaces 83 of the previous example.

[0092] Mathematical modeling of the root ring 80 indicates that a root ring having six times the number of metal to composite fiber interfaces 83 will be six times stronger. Thus, by modifying the dimensions of the metal sheets 33 and by selecting the number of layers in the root ring 80, the strength of the root ring 80 and, by association, the strength of the root 29 of the finished wind turbine blade 10 can be varied and tailored for a particular application. This is advantageous because it allows the design and manufacture of roots 29 of varying strengths without requiring changes to the overall dimensions of the root. This is beneficial for the purposes of standardization and overcoming design limitations imposed by road transport considerations (e.g., the height of a bridge).

[0093] In addition to varying the size and number of layers of metal sheet 33 , the strength of the connection between root 29 and pitch bearing 40 may be varied by varying the number and location of radially extending bolts 45 (if used) and / or by varying the surface finish of metal sheet 33 and interlocking formations (if present).

[0094] The method of winding the sheet 33, 98 onto the mandrel 90 is advantageous because it allows multiple layers to be formed quickly without requiring extensive manual labor. In addition, all or a portion of the metal sheet 33 may be roughened prior to being applied to the mandrel 90 to improve the bond between the metal sheet 33 and the fiber composite material 38 in the finished root ring 80.

[0095] In one example, the metal sheet 33 is overlapped with the sheet-like fibrous material 98 before the overlapped sheets are wound onto the mandrel 90. Thus, once wound onto the mandrel 90, the metal sheet 33 is interlaced with the sheet-like fibrous material 98 in the finished root ring 80.

[0096] In another example, a layer of metal sheet material 33 is wound onto the mandrel 90 followed by an overlapping layer of sheet-like fiber material 98 (or vice versa) such that the metal sheet material 33 is interleaved with the sheet-like fiber material 98 in the completed root ring 80 .

[0097] In each case, the sheet-like fiber material 98 may overlap the metal sheet 33 only in the vicinity of the second portion 36 of the metal sheet 33 to form the transition section 31 of the root ring 80 .

[0098] The sheet-like fiber material 98 may include a pre-impregnated sheet-like fiber material. Alternatively, the sheet-like fiber material 98 may include a dry sheet-like fiber material that is wound around the mandrel 90 before being impregnated with resin and cured. Fig.10 It should be understood that, prior to curing of the pre-impregnated sheet fiber material, or prior to impregnation and curing of the dry sheet fiber material, the segment of the assembled but uncured root ring 80 extending from the transition segment 31 to the tip end 82 of the root ring 80 may be referred to as a fiber segment 88. The fiber segment 88 becomes the composite fiber segment 32 once cured.

[0099] The tapered inner surface 89 of the composite fiber segment 32 of the root ring 80 can be formed during the winding process by winding a sheet fiber material 98 having a greater thickness than the sheet fiber material wound onto the mandrel 90 near the distal end 82 of the root ring 80 onto the mandrel 90 near the transition segment 31. If desired, the cured composite fiber segment 32 of the root ring 80 can be machined to obtain improved dimensional accuracy. In an alternative exemplary method, the fiber segment 88 can be wound onto the mandrel 90 at full thickness (i.e., the same or similar thickness as the metal segment 30 and the transition segment 31), cured, and then machined as desired to provide any particular cross-sectional profile, including a taper.

[0100] The above about Figures 4 to 7c Any of the root configurations discussed above may be used with respect to Figures 9a to 9c Made in the manner described.

[0101] Once completed, the root ring 80 is removed from the mandrel 90 and incorporated into the blade shell 13 to form the root 29 of the complete wind turbine blade 10. In one example, this can be achieved by cutting the root ring 80 in half and incorporating each half into the windward half shell 17 and the leeward half shell 18 of the blade shell 13. In this method, the root ring half is partially or completely placed in the hub end 21 of the half shell 17, 18, covered with fiber material and cured. The two half shells 17, 18 including the root ring half are then connected together to form a complete wind turbine blade shell 13 with a complete root 29.

[0102] In an alternative example, the finished root ring 80 may be integrally incorporated into the blade shell 13 by positioning the complete root ring 80 partially or completely into the hub end 21 of the windward and leeward half shells 17, 18, and connecting the root ring 80 to the half shells 17, 18 by covering with a fiber material and curing. This may be done after the windward and leeward half shells 17, 18 have been connected together to form the blade shell 13. Alternatively, the root ring 80 may be connected to one half shell, after which the other half shell is placed in place and connected to the root ring 80 by covering with a fiber material and curing as previously described.

[0103] In all of the above-described root loop connection methods, the covering fiber material may be a pre-impregnated fiber material or a dry fiber material that is impregnated with resin prior to curing.

[0104] In all the examples described herein, the second portion 36 of the metal sheet 33 located in the transition section 31 of the root 29 or the root ring 80 is linearly tapered or has a substantially constant thickness (optionally with radially extending formations). It should be understood that the second portion 36 of the metal sheet 33 located in the transition section 31 of the blade root 29 or the root ring 80 may have any suitable cross-sectional profile, including a curved profile. The second portion 36 of the metal sheet 33 located in the transition section 31 may taper from one side of the metal sheet 33 so that one side of the curved metal sheet 33 has a linear cross-section. Alternatively, the metal sheet 33 may taper from both sides toward a common vertex.

[0105] The example configurations of roots and root rings described above provide a number of advantages over the prior art. In particular, the strength and stiffness of the root / root ring can be tailored for a particular application by modifying the size and profile of the metal sheet and / or the number of layers of metal sheet. Such changes affect the strength, stiffness and number / surface area of ​​the metal to fiber composite interfaces contained in the root / root ring. Thus, roots / root rings of different capacities can be designed and manufactured without changing the overall dimensions of the root / root ring. This is beneficial for the purposes of standardization and overcoming design limitations imposed by road transport considerations (e.g., the height of a bridge).

[0106] The strength of the connection between the root and the pitch bearing may also be deliberately engineered by varying the number and location of bolts (if used), and / or by varying the surface finish of the sheet metal and interlocking formations (if present).

[0107] Because the metal sections of the root / root ring are much stiffer than the prior art glass fiber roots, the spanwise innermost ends of the carbon fiber spar caps within the blade shell can be positioned closer to the root than was possible in the prior art. Therefore, the stiffness of the entire wind turbine blade can be increased because the carbon fiber spar caps can extend closer to the stiffer root. Furthermore, the metal sections of the root can withstand higher peak loads than is possible with the prior art glass fiber roots, which means that less glass can be used in the construction of the root, which provides cost and environmental benefits.

[0108] An advantage of the above described root structure is also that the integrity of the bond between the various layers of the root / root ring can be interrogated over the full depth of the root wall by ultrasonic non-destructive testing (NDT) methods. This is not possible with a root comprising conventional spanwise extending bolt holes as the ultrasonic NDT equipment cannot be "unaffected" by the voids formed in the glass fiber composite material in which the insert for the stud insert is accommodated.

[0109] The method of winding the sheet onto a mandrel is advantageous because it allows for rapid formation of multiple layers without requiring extensive manual labor. In addition, all or part of the surface of the metal sheet may be treated prior to winding onto the mandrel to increase friction between the layers of metal sheet in the metal segment and to help improve the bond between the metal sheet and the fiber composite material in the finished root ring. The surface treatment may include a mechanical roughening process (e.g., sandblasting) and / or may include a chemical treatment process.

Claims

1. A method of manufacturing a root ring (80) for a wind turbine blade (10), the root ring comprising a hub end (81) and a tip end (82), the root ring extending from the hub end to the tip end in a spanwise direction, the method comprising: winding a metal sheet (33) onto a mandrel (90) to form a metal segment (30) proximate a hub end of the root ring; winding a sheet of fiber material (98) onto the mandrel to form a fiber segment (88) distally proximate the root ring; as well as The metal sheet material (33) is interlaced with the sheet-like fiber material (98) to form a transition section (31) of the root ring, wherein the transition section is located between the metal section and the fiber section.

2. The method according to claim 1, comprising: The metal sheet (33) is overlapped with the sheet-like fiber material (98) and then the metal sheet and the sheet-like fiber material are wound onto the mandrel (90).

3. The method according to claim 1 or 2, comprising: A layer of metal sheet material (33) is wound onto the mandrel (90), followed by a layer of sheet-like fibrous material (98) being wound onto the mandrel.

4. A method according to any one of the preceding claims, comprising: At least a portion of the metal sheet (33) is treated to change the surface characteristics of the metal sheet before the metal sheet is wound onto the mandrel (90).

5. A method according to any one of the preceding claims, wherein: The metal sheet (33) includes a first portion (34) positioned adjacent to a first edge of the metal sheet and a second portion (36) positioned adjacent to a second edge of the metal sheet, wherein a thickness of the second portion gradually decreases from the first portion toward the second edge of the metal sheet, and the method includes: winding the metal sheet onto the mandrel (90) so that the first portion of the metal sheet is located in the metal segment (30) of the root ring (80), and the second portion of the metal sheet is located in the transition segment (31) of the root ring.

6. A method according to any one of the preceding claims, wherein: The sheet-like fiber material (98) comprises a pre-impregnated sheet-like fiber material, wherein the method comprises curing the pre-impregnated sheet-like fiber material after the pre-impregnated sheet-like fiber material has been wound onto the mandrel (90).

7. A method according to any one of the preceding claims, wherein: The sheet-like fibrous material (98) comprises a dry sheet-like fibrous material, wherein the method comprises: impregnating the sheet-like fibrous material with a resin after the sheet-like fibrous material has been wound onto the mandrel (90); and curing the resin.

8. A method according to any one of the preceding claims, comprising: A sheet of fiber material (98) having a thickness greater than that of the sheet of fiber material wound onto the mandrel at one end of the fiber segment near the distal end of the root ring is wound onto the mandrel (90) at the opposite end of the fiber segment (88) near the transition segment (31), so that the thickness of the fiber segment gradually decreases toward the distal end of the root ring.

9. The method according to any one of the preceding claims, comprising: The outer surface of the fiber segment (88) is machined to form a tapered wall thickness profile in the fiber segment of the root ring.

10. A method of forming a wind turbine blade (10), the method comprising: forming a root ring (80) using the method of any one of the preceding claims; removing the root ring from the mandrel (90); Providing a windward half shell (17) and a leeward half shell (18) of a wind turbine blade shell, wherein the windward half shell and the leeward half shell each include a hub end (21) and a tip end (19), wherein each half shell extends in a span direction from the hub end to the tip end; connecting the windward half shell to the leeward half shell to form a wind turbine blade shell; Positioning the complete root ring at the hub end of the windward half shell and the hub end of the leeward half shell; and The root ring is connected to the windward half shell and the leeward half shell.

11. The method according to claim 10, wherein: Positioning the root ring (80) at the hub end (21) of the windward half shell (17) and the hub end (21) of the leeward half shell (18) includes positioning the root ring at least partially between the windward half shell and the leeward half shell.

12. The method according to claim 10 or 11, wherein: Connecting the root ring (80) to the windward half shell (17) and the leeward half shell (18) includes: laying one or more sheets of fibrous material over the intersections between the root ring and the windward and leeward half shells; and The resin that has penetrated or impregnated the fiber material sheet is cured.

13. The method according to any one of claims 10 to 12, wherein: Connecting the root ring (80) to the windward half shell (17) and the leeward half shell (18) includes connecting the root ring to one of the windward half shell or the leeward half shell and then connecting the root ring to the other of the windward half shell or the leeward half shell.

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